Patent GB-661229-A (GB)
Title: Improvements in and relating to multi-channel electric pulse-signalling systems
Inventor: LEVY MAURICE MOISE
IPC: H04J3/10
Filed: 1949-03-09
Abstract: 661,229. Multiplex pulse signalling. GENERAL ELECTRIC CO., Ltd. June 8, 1950 [March 9, 1949], No. 6454/49. Class 40 (v). The three or more interlaced channel pulse trains of a multi-channel signalling system are arranged so that the channel numbers of the pulses adjacent successive pulses of any one channel follow a cyclic variation, in order to reduce the effect of cross-talk. In one embodiment, a 36-channel system consists of two groups, one containing the odd channels of a 32-channel system with a recurrence frequency of 10 kc/s., and the other the even channels of a 40-channel system with a recurrence frequency of 8 kc/s. The output of a 10 kc/s. master oscillator 10, Fig. 1, deflects the beams of two cathode-ray distributers 11, 12, each having four anodes D1 . . . D4 and D1<SP>1</SP> . . . D4<SP>1</SP>, respectively, arranged so that the pulses from the two groups are 45 degrees out of phase. The output from oscillator 10 is also frequency multiplied in circuit 13 to 40 kc/s. to deflect the beam of distributer 14 and further multiplied in circuit 15 to 160 kc/s. to be applied to the control grid of tube 14. At the anodes E1 ... E4 of tube 14, appear interlaced trains of short pulses at a recurrence frequency of 40 kc/s. The pulses from E1 are fed to a frequency divider 16 producing pulses at 8 kc/s. which after shaping in circuits 17, 18, 19 produce a wave of frequency 8 kc/s. which deflects the beams of two distributers 20, 21. Each of these tubes has four anodes V1 ... V4 and V1<SP>1</SP> ... V4<SP>1</SP>, respectively, arranged so that the pulses from the two groups are 45 degrees out of phase. The wave from circuit 19 is also fed to a frequency multiplier 22 which produces a 32 kc/s. wave to deflect the beam of distributer 23, the grid of which is fed with a second antiphase wave from the 160 kc/s. source 15 and which has five anodes, E1<SP>1</SP> ... E5<SP>1</SP>, which produce interlaced trains of short pulses at a recurrence frequency of 32 kc/s. These pulses interlace those from the anodes E1 . . . E4 of distributer 14. The channel modulating signals of the sixteen odd channels of the 32-channel system are fed to the control grids of pentodes 37 ...52, Fig. 3, arranged in four groups 24 ... 27 of four, from input terminals C1, C3, C5 ... C31, arranged as shown. The groups 24 ... 27 each have a common anode circuit feeding respectively the deflecting electrodes of four known cathode-ray pulse time modulators 28 . . . 31 having a common output 53. The suppressor grids of the four valves in groups 24, 25 are fed with pulses from anodes D1 ... D4, Fig. 1, and those of groups 26, 27 with pulses from anodes D1<SP>1</SP> ... D4<SP>1</SP>, while the control grids of tubes 28 . . . 31 are fed with pulses from anodes E1 ... E4, respectively. The resulting interlaced channel pulse train contains the channel pulses in the order 1, 3, 5, 7, &c. to 31. A similar circuit produces the pulses of the twenty even channels of the 40-channel system in the order 2, 4, 6, &c. to 40, which interlace with the first group, to produce the required cyclic change in the channel order in the combined pulse train. Channels 1 and 2 are normally used for the transmission of different synchronizing signals for the two groups, which may consist of pulse pairs with different spacing. In another embodiment, providing three channels of a six-channel system, the pulses in two of the channels are non-regularly recurrent. The output of a generator 54, Fig. 4, consisting of a square wave G, Fig. 5, is applied to modulators 55, 56, 57, to which the respective channel modulating signals are applied from terminals 58, 59, 60. Gating circuits 61, 62, 63, respectively, are interposed between the modulator outputs and the common terminal 64. To circuit 61 are applied, at terminals 65, 66, the waveforms H1, H2, coincidence of the positive portions of waves G, H1, H2 producing output channel pulses H3 which are non-regularly occurring. Circuit 62 is gated open by pulses J1 applied to terminal 67 which results in the production of channel pulses J2 at its output. To circuit 63 are applied, at terminals 68, 69, the waveforms K1 H2, so that the output channel pulses K2 are produced, which are also non-regularly recurrent. The time modulation, thus introduced, of pulses H3 and K2 can be arranged to fall outside the signal frequency band and may be filtered out.